 .model small
.stack
.data
Message db "Press Y or N:$" ;Prompt for user
Uyes db "You pressed Y!$" ;Pressed y
Uno db "You pressed N!$" ;Pressed n
 
;how to do assembly:
;download masm32
;download link563.exe (extracts link.exe)
;replace c:\masm32\bin\link.exe with THAT link.exe
; use ml /c /coff blah.asm
;  then    link blah.obj
; when it asks you for blah.exe  just keep hitting enter.
 
 
.code
_start:
mov ax,03h ;clears screen (function 3h)
int 10h ;interrupt 10h

mov ax, SEG Message ;put segment of message into AX
mov ds, ax ;put this into DS
mov dx, OFFSET Message ;put offset of message into AX
mov ah,09h ;Function 9h of
int 21h ;Interrupt 21h
 
mov ah,01h ;function 01h of int21h,
int 21h ;get char from keyboard
 
cmp al, "Y" ;if ah Y then
je Yes ;Goto Yes label
 
cmp al, "N" ;if ah N then
je No ;Goto No Label
jne _start ;if not Y or N then goto start
 
Yes:
mov ax,03h ;clears screen (function 3h)
int 10h ;interrupt 10h
 
mov ax, SEG Uyes ;segment of Uyes
mov ds, ax ;put segment into DS
mov dx, OFFSET Uyes ;put offset of Uyes into DX
mov ah,09h ;function 9h print string at DS:DX
int 21h ;call interrupt 21h
jmp close
 
No:
mov ax,03h ;clears screen (function 3h)
int 10h ;interrupt 10h
 
mov ax, SEG Uno ;segment of Uno
mov ds, ax ;put segment into DS
mov dx, OFFSET Uno ;put offset of Uno into DX
mov ah,09h ;function 9h print string at DS:DX
int 21h ;call interrupt 21h
jmp close
 
close:
mov ax,4c00h ;put 4c00h into ax, closing back to DOS
int 21h ;INT 21h, return to DOS
 
end _start

created 1 year ago

Assembly Online Compiler

Write, Run & Share Assembly code online using OneCompiler's Assembly online compiler for free. It's one of the robust, feature-rich online compilers for Assembly language. Getting started with the OneCompiler's Assembly compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as Assembly and start coding.

About Assembly

Assembly language(asm) is a low-level programming language, where the language instructions will be more similar to machine code instructions.

Every assembler may have it's own assembly language designed for a specific computers or an operating system.

Assembly language requires less execution time and memory. It is more helful for direct hardware manipulation, real-time critical applications. It is used in device drivers, low-level embedded systems etc.

Syntax help

Assembly language usually consists of three sections,

Data section

To initialize variables and constants, buffer size these values doesn't change at runtime.
bss section

To declare variables
text section

_start specifies the starting of this section where the actually code is written.

Variables

There are various define directives to allocate space for variables for both initialized and uninitialized data.

1. To allocate storage space to Initialized data

Syntax

variable-name    define-directive    initial-value

Define Directive	Description	Allocated Space
DB	Define Byte	1 byte
DW	Define Word	2 bytes
DD	Define Doubleword	4 bytes
DQ	Define Quadword	8 bytes
DT	Define Ten Bytes	10 bytes

2. To allocate storage space to un-initialized data

Define Directive	Description
RESB	Reserve a Byte
RESW	Reserve a Word
RESD	Reserve a Doubleword
RESQ	Reserve a Quadword
REST	Reserve a Ten Bytes

Constants

Constants can be defined using

1. equ

To define numeric constants

CONSTANT_NAME EQU regular-exp or value

2. %assign

To define numeric constants.

%assign constant_name value

3. %define

To define numeric or string constants.

%define constant_name value

Loops

Loops are used to iterate a set of statements for a specific number of times.

mov ECX,n
L1:
;<loop body>
loop L1

where n specifies the no of times loops should iterate.

Procedures

Procedure is a sub-routine which contains set of statements. Usually procedures are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

procedure_name:
   ;procedure body
   ret